1. Field of the Invention
The present invention relates to a composite molding device applicable at the same site for preforming a closed-end parison or controlling the temperature of the closed-end parison as well as stretch blow molding the preform or temperature-controlled parison to a final product, such as a bottle.
2. Background Art
Two different methods are applicable to the process of injection and stretch blow molding, which releases an injection-molded, closed-end parison from an injection mold immediately after conclusion of injection molding and manufactures a hollow article, such as a vessel, by stretch blowing the still warm closed-end parison. One method manufactures a final product by the process of stretch blow molding (may be referred to as primary blow molding) after molding the parison released from the injection mold to a preform corresponding to an intermediate or controlling the temperature of the parison. The other method directly prepares a final product from the parison by the process of stretch blow molding.
The injection-molded parison is placed into either a preform mold or a temperature control mold, which is interposed between an injection mold and a blow mold, for preforming or temperature control of the parison prior to the primary blow molding. The temperature control may be implemented through the preforming process.
The injection and stretch blow molding process having either the preforming step or the temperature control step requires four stations; that is, an injection-molding station, a preforming or temperature-control station, a primary blow molding station, and a product release station. Each station requires a set of neck mold in order to realize the simultaneous operations at the respective stations; that is, a total of four sets of neck mold also functioning as transport members of the parison or the final product are required.
Such a 4-station molding device including a preforming or temperature-control station is greater in size than a 3-station molding device for directly stretch blow molding an injection-molded parison to a final product, and requires one additional set of neck mold. In a structure adopting a rotary table as transport means, a problem of inertia arises in the course of rotating shift due to the increased diameter and weight of the bulky device.
A temperature-controlling, blow molding device has been developed in order to solve this problem, where temperature control of a parison and stretch blowing are executed at an identical site (see Japanese Patent Laid-Open Publication No. 60-247541). The device includes a pair of clamping plates mounted on a slidable seat member arranged on a table, and separate temperature-control mold half and blow mold half disposed in parallel inside the pair of clamping plates. A lateral or horizontal shift of the seat member alternately moves the temperature control mold and the blow mold with the pair of clamping plates with respect to a parison supported by a neck mold, so as to implement the temperature control process and the stretch blowing process without moving the parison.
A molding machine having the conventional temperature controlling, blow molding device requires three operation stations with three sets of neck mold. Since the temperature control mold and the blow mold are arranged in parallel inside the same pair of clamping plates, the width of the clamping plates in this molding machine is substantially twice the width of clamping plates on a 4-station device. Even when the width of the clamping plates on the 3-station machine is within a table dimension, leftward and rightward lateral shifts during the molding process require the blow molding device on the table to have a sufficiently large area allowing the lateral shifts.
Lateral shifts of clamping plates do not require a much additional area in a small-sized molding machine applied for simultaneously manufacturing a less number of small articles. A mass-producing, molding machine applied for simultaneously producing a large number of articles or a large-sized molding machine applied for manufacturing bulky articles like 20 l-bottles has clamping plates of a remarkably greater width than those applied for the small production, and it is extremely difficult to set the sufficient area allowing lateral shifts on the table because of the preferable orientation of operation stations.
This structure shifts an extremely large mass, that is, a clamping device as well as the clamping plates and the molds on the seat member, and accordingly requires a powerful shifting device. This structure is thus applicable only to small-sized molding machines and is not suitable for stretch blow molding devices used for the purpose of mass production or production of large articles.